The generation of electrical energy by the use of wind turbines is a field which is expanding to an ever greater extent. Because of this massive expansion there are only a limited number of sites for wind turbines, which means that to an increasing degree smaller wind turbines are being replaced by ones giving higher outputs. Another trend is for wind turbines to be installed in off-shore coastal regions. It is here that wind turbines giving the highest outputs are generally installed. Higher outputs call for bigger wind turbines and these thus have to have rotors of diameters from 80 to 160 m. A rotor blade comprises a rotor blade root to connect the rotor blade to the hub of the rotor and a rotor blade aerofoil. The rotor blade aerofoil is intended to convert the kinetic energy of the wind into a rotary movement of the rotor in the optimum way. The rotor blade root serves to transmit the torques involved to the hub of the rotor and hence to the generator of the wind turbine.
Up to a rotor diameter of approximately 80 m, it is often fibre-reinforced plastics composites based on a plastics material reinforced with glass fibre which are used. At larger rotor diameters of more than 80 m it is a combination of glass-fibre reinforced plastics materials (GFRP) and carbon-fibre reinforced plastics materials (CFRP) which is used. However, this hybrid construction is very cost-intensive. The aim of the hybrid construction is to keep the deflection or bowing of the individual rotor blade as low as possible when under load when the rotors are of these extreme diameters. Another problem is the system for protecting rotor blades against lightning, which imposes additional costs when rotor blades of the said hybrid construction are being produced. What is more, the pressure from costs is already high when wind turbines are being produced, particularly ones in the higher output ranges. To solve this problem there is a rotor blade for wind turbines known from German unexamined patent application laid open to public inspection DE 10 2007 036 917 which has stressing members arranged in the rotor blade which place a spar provided in the rotor blade under compressive stress, thus minimising stress-dependent deformations due to wind loads. On the one hand a combination of CFRP and GFRP plastics materials is used even in this solution and on the other hand this solution, too, does not have an integral system for protection against lightning.